SimpleConvertImage.java:7: warning:com.sun.org.apache.xerces.internal.impl.dv.util.Base64 is internal proprietary API and may be removed in a future release
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
^

SimpleConvertImage.java:16: warning: com.sun.org.apache.xerces.internal.impl.dv.util. Base64 is internal proprietary API and may be removed in a future release
String base64String=Base64.encode(baos.toByteArray());
^

SimpleConvertImage.java:19: warning: com.sun.org.apache.xerces.internal.impl.dv.util .Base64 is internal proprietary API and may be removed in a future release
byte[] bytearray =Base64.decode(base64String);
^

代码如下

import java.awt.image.BufferedImage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import com.sun.org.apache.xerces.internal.impl.dv.util.Base64; 
public class SimpleConvertImage {
    public static void main(String[] args) throws IOException{
        String dirName="/root/Desktop";
        ByteArrayOutputStream baos=new ByteArrayOutputStream(1000);
        BufferedImage img=ImageIO.read(new File(dirName,"Screenshot.png"));
        ImageIO.write(img,"png",baos);
        baos.flush();

        String base64String=Base64.encode(baos.toByteArray());
        baos.close();

        byte[] bytearray =Base64.decode(base64String);

        BufferedImage imag=ImageIO.read(new ByteArrayInputStream(bytearray));
        ImageIO.write(imag,new File(dirName,"snap3.png"));
    }
}